Production and esterification of esterifiable nitroparaffin derivatives



raonucrron AND ss'rnnrrrca'rros or ESTELE mm? s: 'rzvEs DERIVA- Andrew McLean, West Kilbride, Scotland, as

slgnor to Imperial Chemical Industries Limited. a corporation of Great Britain No Drawing. Application April 3, 1944, Serial No. 529,400. In Great Brl April 16', 1948 3 Claims. (Cl. 260-638) The present invention relates to a new or improved method for the preparation of valuable mixtures comprising certain esteriflable, more particularly methylolated, nitroparaflin derivatives, in solution in liquid aliphatic polyhydric alcohols. The invention also includes the chemical reaction products obtained from the said mixtures, more particularly their esterification products and-especially the explosive nitric ester products resulting from their nitration. The invention permits or the production of the said mixtures in a simplified manner and/or of the production of such mixtures of improved quality and better suited for converslondnto the said chemical reaction products.

The esteriflable nitroparaflln derivatives wit which-the present invention is concerned are those in the molecule whereof at least one hydrogen atom attached to the carbon atom directly bound to the nitro group is replaced by a methylol group. Such methylolated derivatives, which include for instance, monomethylol-nitromethane, monomethylol-dimethyl-nitromethane, dimethylol-nitromethane, trimethylol-nitromethane, dimethylol-nitroethane, are customarily prepared by chemical reaction between a nit! oparaflln and formaldehyde in presence of a basic catalyst. A number of them have been used experimentally as materials to be nitrated for the production of explosive nitric esters, and various other applications ior these methylolated nitroparafiin derivatives have been suggested. Diillculty has been experienced in washing the liquid nitric esters of the methylolated nitroparaflln derivatives after their removal from the refuse nitrating acid employed, owing to the fact that they very easily emulsiiy with the washing water, much more readily than many other'liquidmitric esters, for

instance those of the p lyhydric alcohols. Partly owing to the small scaleon which the methylolated nitroparaflin derivatives have been made, and partly on account of their cost, their explosive nitric esters have frequently been associated with liquid explosive esters of polyhydric alcohols, -for instance nitroglycerine. It is known that it is convenient to subject a solution of the methylolated nitroparaihn derivative in the liquid polyhydric alcohol to nitration in order 'to produce the desired liquid nitric ester mixture. The washing 0! the resulting liquid nitric ester mixture is, as might be expected, less easily accomplished than that 01 the nitric ester of the polyhydric alcohol although not so much'so as that of the liquid nitric ester of the methylolated nitroparafiin derivative.

- methane by condensing nltromethane withformdehyde,

The methylolated nitroparaflin derivatives are extremely soluble in water; and when the condensation reaction between the nitroparaffln and formaldehyde leading to their formation is conducted in water as a reaction medium, soluble by.- products are often formed, and it is necessary to concentrate the aqueous reaction mixtures to a syrup in order to cause them to crystallise out. A good yield of product of high quality is not usually obtained; and, especially if evaporation is carried out at ordinary pressure, some decomposition takes place which adversely sheets the quality of the methylolated nitroparafl'ln derivatives. Similar disadvantages occur if methyl or ethyl alcohol isused as solvent. These disadvantages have been found tobe particularly prominent in the case of poly-methylol derivatives containing the maximum number of methylol groups, which are those most frequently desired. 1

In order to overcome these disadvantages it has been proposed to prepare trimethylol-nitroaldehyde, especially in the form of paraformalin an alkaline medium comprising a monohydric aliphatic valcohol containing 4 to 6 carbon atoms, crystallising the resulting compound from the monohydric alcoholic solvent and washing and drying the resulting crystals. A better yield'of a purer product is thereby obtained. This process has the technical disadvantage that if the monohydric alcoholic solvent employed is not to be lost, then arrangements must be made for its recovery, and that when the trimethylol nitromethane is nitrated in admixture with a liquid polyhydric alcohol the tendency to emulsification or the mixed nitric esters while they are being washed is still very noticeable.

We have now found that the reaction between the 'nitroparafiln and the formaldehyde may be conducted in a reaction medlum'consisting of the aliphatic polyhydric alcohol whereby not only is the inconvenience of isolating the methylolated nitroparaflln derivative from the reaction mixture avoided, and the recovery of a volatile solvent rendered unnecessary but the resulting solution containing the methylolated nltro-paramn derivativeand the aliphatic polyhydric alcohol is of improved quality as evidenced by the fact that the liquid nitric ester mixture obtained from it is not substantially more liable to emulsify during washing than the liquid nitrate of the polyhydric alcohol. p v

, According to the present invention therefore a method for the preparation of methylolated iective than soda alkalis, while lime has been cule oi the nitroparaiiin, which will frequently be lowing examples, in which the parts are parts by .aiiln and the formaldehyde in a medium comprising, at least one aliphatic polyhydric alcohol.

In putting the invention into eflect, the iorm aldehyde may conveniently be employed in the form '0! paraformaldehyde, and'the reaction is preferably carried out in the presence of a basic catalyst, of which only a very small proportion is required, the quantity being less than that which will darken the nitroparamn. It has been found that thepotash alkali catalysts, e. g. potassium hydroxide and potassium carbonate, are more effound of little use. The quantity or formaldehyde employed is preferably very close to the theoretical calculated quantity for the number of methylol groups to be introduced into the molethetheoretically' possible maximum. The reaction may conveniently be allowed to proceed at raised temperature, and after the reaction is'complete, the mixture may be rendered no longer alkaline by the addition or a concentrated or anhydrous acid. If desired it may then be illtered, and the resulting liquid is then ready-tor esteriflcation if it is to be converted into an ester mixture, e. g. by acetylation, nitration or the like in known manner.

Part of the polyhydric alcohol, e. g. glycerol, may advantageously be used as a diluent tor the nitro-paraflin, e. g. nitro-methane, a corresponding part being omitted from the glycerol in the reaction vessel in which the methylolation is to take place, which may contain all the remaining ingredients.

The invention is further illustrated by the folweight.

Example 1 I To 160 parts glycerine of dynamite quality there are added 25 parts parai'ormaldehyde and 0.2 part potassium hydroxide. The mixture is 45 stirred and'the temperature is raised to 50 C. at which it is held until the potassium hydroxide is dissolved, which may take about V 01 an hour, by which time the paraiormaldehyde is also largely in solution. 16.parts nitro-methane are then so slowly added. with continued stirring, and when the temperature or the reaction mixture begins to rise, the external heating is dispensed with. The temperature or the mixture is controlled by the rate of addition of the nitro-methane so that it 55 does not exceed 70 C. when the reaction is over, as indicated by a fall in thetemperaure, the potassium hydroxideis destroyed'by the addition of suiilcient concentrated sulphuric acid to make themixture Just acid. Atthls stage the mixture is clear and littleor no diil'erent in colour from the glycerine employed. The hot liquid is filtered and when cool can be nitrated in the manner commonly used for the manufacture of nitroglycerine.

- Example 2 ine while the other 16 parts of gLvcerine are used 70.

2,eee,eee

as a diluent for the 16 parts of nitro-methane. The nitro-methane is thus added as a solution in glycerine.

Emmple 3 The ingredients are the same as in Example 1 except that the glycerine is replaced by an equal weight of ethylene-glycol. The mixture of the ethylene-glycol, paraiormaldehyde and potassium hydroxide is stirred together for /2 an hour at 20 C. and the nitro-methane is then added over a'period of 20 to 30 minutes. The temperature rises to about C. and after some time the solution becomes clear, indicating that the paraiormaldehyde has been used up. When the temperature begins to fall the solution is acidified with concentrated sulphuric acid and the hot liquid is filtered to remove insoluble matter.

Example 4 The reagents used are the same as in Example 1, except that the glycerine is replaced by its own weight of di-glycerine. The preparation is conducted otherwise as in Example 1.

In the foregoing examples the methylolated nitro-paraiiin is trimethylol-nitromethane.

Example 5 The mixture is stirred oi the approximate composition nitro-methane l5 per cent, nitro-ethane 8 per cent, l-nltropropane 37 per cent, 2-nitropropane 40 per cent are then added with continual stirring. The temperature commences to rise, and external heating is dispensed with when this is observed. The rate of addition is controlled so that the temperature does not exceed C. The end of the reaction is heralded by a tendency to the clearing of the solution and slight fall in temperature.

The mixture is then reheated to the maximum temperature it had attained during the reaction and maintained at this temperature for half an hour, by which time it should have no smell of formaldehyde. The warm solution is filtered, and yields a clear liquid which, when cooled, is suitable for nitration.

I claim:

1. A method for the preparation of methylolated nitroparaflln derivatives in solution in liquid aliphatic polyhydric alcohol which comprises conducting the condensation reaction between the nitro-paraflin and the formaldehyde in a medium comprising at least one aliphatic poly-hydric alcohol.

2. A method as claimed in claim 1 wherein the formaldehyde is employed in the form oi paraformaldehyde.

3. A method as claimed in claim 1 wherein the reaction is carried out in the presence or a potash alkali catalyst.

ANDREW McLEAN. 

